Question

There are 2.2 pounds in a kilogram. if a boys mass is 40kg, what is his height in pounds?

Answer 1

There are NOT 2.2 pounds in a kilogram. 
Any teacher who makes such a statement is misleading you, and
putting things into your head that will be tough to get rid of later.

2.2 pounds is the approximate WEIGHT of 1 kilogram of MASS
on Earth.  The SAME KILOGRAM of mass weighs about 5.8 ounces
on the Moon, and about 11.8 ounces on Mars.

If a boy's mass is 40 kg, then he weighs about 29.2 pounds on Mars,
about 14.7 pounds on the Moon, and about 89 pounds on Earth.

"Height" doesn't belong anywhere in this question.

Answer 2

The simplest way to do this is to set up equivalent fractions, like this- 

$\frac{1}{2.2}$ = $\frac{40}{x}$

Solve for x by using cross multiplication.

40*2.2= 88
1*x=88
x=88

Therefore, the boy weighs 88lbs.